Switching arrangement for combined manual and automatic telephone systems



June 5, 1951 s. E. PETERSON ET AL 2,556,103

SWITCHING ARRANGEMENT FOR COMBINED MANUAL AND AUTOMATIC TELEPHONE SYSTEMS Filed Nov. 9, 1946 s Sheets-Sheet 1 n 15 I I0 .J Fri 4, a m E i (D- LL.

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ATTORNEY s. E. PETERSON ET AL 2,556,103 SWITCHING ARRANGEMENT FOR COMBINED MANUAL A AND AUTOMATIC TELEPHONE SYSTEMS 3 Sheets-Sheet 2 INVENTORS. SETH E. PETERSON MORRIS E. GRIFFINS iulil 3N N3 i A 3N E A 03 m 5 5mm 6 EN 6 Filed Nov. 9, 1946 June 5, 1951 ATTORNEY June 5, 1951 s. E. PETERSON ET AL SWITCHING ARRANGEMENT FOR COMBINED MANUAL AND AUTOMATIC TELEPHONE SYSTEMS 3 Sheets-Sheet 3 Filed Nov. 9, 1946 m o E3050 mohouzzoo IN VEN T 0R5. SETH E. PETERSON MORRIS E. GRIFFINS ATTORNEY? Patented June 5, 1951 SWITCHING ARRANGEMENT FOR COM- BINED MANUAL AND AUTOMATIC TELEPHONE SYSTEMS Seth E. Peterson, Bogota, Colombia, and Morris E. Griffins, Riverside, Ill., assignors to Associated Electric Laboratories, Inc., Chicago, 111., a corporation of Delaware 7 Application November 9, 1946, Serial No. 708,974

13 Claims.

This invention relates to telephone systems in general and is concerned particularly with improvements in the circuit and apparatus employed in arranging a manual telephone system for partial automatic operation.

The problem of providing either manual or automatic service in a telephone system is complicated by the fact that automatic switching equipment is commonly operated on a higher voltage than that employed for manual switching equipment and by the further fact that the polarity for testing and guarding in automatic equipment is reversed as compared with the usual manual equipment. These factors present substantial difficulties, particularly when both automatic and manual lines are to be permanently retained in the system.

It has been common practice, when both automatic and manual lines are operated in the same telephone system, to route calls from automatic lines to manual lines by way of operator positions. When the calls originate on manual lines, special equipment is provided in the operator positions, or special operator positions are provided for completing calls to automatic lines.

The present invention provides for direct access to all of the lines in the system by both the automatic lines and the operator positions. Lines which are to have manual service utilize a standard manual line circuit and require no modification except the connection of a multiple of the line and test conductors to the proper automatic equipment. Lines which are to have automatic service are supplied with an automatic line circuit which is connected to a, manual circuit with only a slight modification of the latter. The line conductors and a test conductor of automatic lines ar multipled to jacks appearing at the operator positions. on automatic lines are routed by way of the automatic switch train directly to either manual or automatic lines. Calls Originating on manual lines are extended by way of the operator positions and the jack multiple directly to either manual or automatic lines.

The primary object of the invention is to provide an improved method Of interconnecting manual and automatic telephone switching equipment, thereby facilitating the use of both manual and automatic subscriber lines in the same telephone system.

It is another object of this invention to provide automatic switching equipment which can Calls originating be connected to a manual telephone system witha minimum amount of modification of the manual switching equipment.

It is a further object of this invention to provide automatic switching equipment which permits manual lines to be readily converted to auto matic operation.

It is another object of this invention to provide automatic switching equipment which has substantially the same test and guarding features as a manual system.

A feature of this invention is that the connector switches in the automatic switch train are arranged to switch thru when ground is encountered on the test conductor and to test busy when a relatively low negative potential is encountered on the test conductor.

Another feature of this invention is that a line seized at the manual switchboard or by the automatic switch train will test busy at all of its multiple appearances at the manual switchboardand in the automatic switch train.

A further feature of the invention is that when an automatic line is taken for use in originating a call it immediately is made busy to the manual switchboard.

The objects and features of this invention together with the operation of the circuits and apparatus embodying the same, will be described hereinafter, reference being had to the accompanying drawings, comprising Figs. 1 to 3 in clusive. The drawings should be arranged with Fig. 2 below Fig. 1 and with Fig. 3 to the left of Fig. 1.

Referrin now to Fig. 1 there is shown by means of the usual circuit diagrams manua1 substations MI and M2 connected over lines L32 and L33 respectively to line equipment and to jacks Hi8 and H8 respectively. The conductors of the jack Hi8 are connected to the contacts 313, SM and 315 in the connector D, Fig. 3, and the conductors of the jack H8 are connected to the contacts 382, 383 and 384 in the connector D, Fig. 3. While only one jack and one set of connector contacts are shown for each line it is to be understood that each line may be multipled to similar jacks in other operator positions and to similar contacts in other connectors. The automatic substantions Al and A2, also shown in Fig. l, are similar to the substations MI and M2 except that they are equipped with dials. The substations Al and A2 are connected over the lines L34 and L35 respectively to line equipment and to jacks I28 and I48 respectively. The conductors of the jack I28 are multipled to contacts 319, 330 and 38! in connector D, Fig.3 and the line conductors of the jack 28 are multipled in addition to the contacts 221 and 228 in the finder B, Fig. 2. The conductors of the jack M8 are multipled to contacts 316, 311 and 318 in connector D, Fig. 3 and the line conductors of the jack [48 are multipled in addition to the contacts 221i and 225 in the finder B, Fig. 2. It is to be understood that these jacks and contacts may be multipled to similar jacks and contacts in the switchboard.

The cord circuit A, also shown in Fig. 1, is one of a number provided at the operatorpositions of the :manual switchboard. The cord circuit A is ofthe conventional common battery type employing a condenser-impedance transmission bridge. which are suitable for connecting ltDfth'E lines, such as lines L32 and L34 by way of the jacks such as the jacks I03 and I28. The cord circuit A is connected to the OpBEEJtOIESTLBIEDhOHG Circuit I12 by the operation of the key I69, and ringing potential is applied'to 'a'called line thru the plug I19 by the operation of the key I11.

The apparatus shown insFi-g..ris :asskeleton finder and selector by means of which automatic substations, such as the substation A2 have access to connectors, such as the connector D. :While only one finder, ?B, and one :selector, C, are shown ;other .similar finders and selectors 5.31118 provided :each .1 having access to :substations such as the substation A2 and Eto @connectors .suchzas the :connector D.

:In Fig. .3 is;shown'a .connector D, which is similarztozthewe'll known fitrowger-zvertical and trotary :type ,suchxas described 'iniPatent'i2g0'40 ,1'5'3 granted IMay 12, 51936 to :Seth Peterson. "The connector D differs: from the I ordinary -Strowger -iconnector .in :that :a.: negative "potential, equal to .the :,negative zpotential used :for operating the -manu'a'l -tsWitchboard, is 1 connected thru resistor 13.6.3 i-andjstutilizedfifor the testing and guarding operations of the connector. The connector 13 :has access ito '3 both :automatic and;:manual substations, ,suchzaaMz and A2, midis-accessible 2130 automaticsubstationszsuchxas A2 by way of finders such as finder B and selectors such as .selector C.

Assume: now that a call .is to :be ;made :.from *the substation MI. ,The receiver *at the :sub- .stationiMI is removed operating the.:1ine:relay .[05'511'0111 groundthru armature .102, thruuthe :line L32 -and the isubstation'gMIgthru armature 1.0.1 eandi'the winding-of the line relay I205 to battery. The line relay I05, at armature .105, -.,closes :;a ,circuit ;to the lamp .101 which "lights, .signallingxthe switchboard that a .call is :wait iing. ,=Assume now that the ccor'd circuit iA-Lis used :fOI answering :the call. The plug I63 :is in- .=,serted;in=:theijack {H38 and'rbattery thru the windins .of the :relay 5160,.t1'i1'll'tl3h6 lower I conductor .ofthe plu I613 :is .aconnected to the contact 21315 :making the lline L32 busy to theconnectorsD. Ihe rout-off relay I 0B is operated from :ground -thruiits gown winding; thru :the .lower :conductor :Qf ithe [plug 15.3 and "the :winding :of the :relay lfil! ato battery, :disconnectingthe"line'rrelay In?" 'from theyline L32 --at;-armature I II I and .discon meetin round ;from :the? line L32 :at :a'rmature :I1Il2. e'I-haline relay I 05. restores 'andsextinguish'es ithe zlamp H01 ;at':armatur.e 166. .A circuit may snow be tracedifromztbatteryithru-the lower Wind-- 5138' :of :the irelay 1M5, :center conductor of the :Pl l 1.63, thrurthefiline :L32 rand thersubstation "MI, upper :conductor of the plug I63gand the upper-winding of the i relay :I 65 to. ground. The relay I65 opei-"atesancl opens a circuit to the lamp .452 at armature I65. The irelay 11:60 101)- .eera'ted iinrseries with the "cut-off relay --I 00 1 rparesra circuitito the lamp I62 :atarmature I61.

'lThe. operator now-connects the operators tele- Qhone 112 :.to the cord circuit A by operating :thfi ikey :I69:and a transmission circuit'is established x-be'tween the substation :MI and the operatorh wztelephoneethru tthe condensers :I61 and 1 58- The ;operator;-now ascertains the :connection desired by the substation-Ml and extend It terminates in the plugs 1.6.3 an d L19 4 the connection by inserting -the .plug I19 into the j ack :associated with the called fisubstation. Assuming that the substation AI is desired, :the operator first contacts the upper conductor of ,the pluglle .to the lower conductor of the jack. I28, 'tozwhich the cut-off relay I20is connected. If ;the 'line L34 is not busy ground thru the winding of the cut-off relay I20 and the armature I38 isencountered on the test conductor and as this is connected thru the upper :conductor of the plug I19 thru the upper winding *ofthe relay I15 to ground no current will flow ethru thisicircuit. This absence of current flow indicates to the operator that the line L34 is *notbusy and the plug 519 is inserted into the jack I28. A circuit may now be traced from battery thru the winding of 'the relay lla-lower -conductor'of the :plug Ililparmature I38 and the windingof the cut-off relay I25, to'ground. 'Therelay I15operates and closesa circuit irom ground thru armatures Hi and I16 and the lamp 'I18'=to "battery causing the lamp I18 to light. The cut-off relay 12d operates, disconnects -ground 'from'theline L34 at armature I22 and idisconnects the line relay I25 from thelinelj3 atiarmature 'I2i. Battery thru the windingof the-relay 115 is connected to the contact '38! tmaking the line L34 busy to the connector D. The operator operates the'key I11 connecting ringing potential from the generator GEN over the-upper and center conductors-ofthe plug 119 and the'line 1.34 to signal the substation 'Al. The keys I11 and I59 are-then restored and the -lig'h-tedlamp llsserves as an indication to the :operator'of the unanswered condition of the call. when the receiver is removed at-the substation AI lthe relay I 1ll 'is operated from battery thru .its lower winding, center conductor of the plug I 19, 'thru theline'L3 I and the substation AI, upper conductor of the plug I19 and the-upper windingof the relay I10 to ground. The relay I10 opens the c'ircuit'to the lamp I18 at armature l 'l l, thus-signalling the operator that the callhas "been answered.

"When the conversation is ende'd'the receiver at the substation M9 is replaced allowing 'the' relay 165 to'restore. Ground thru'armatures I 66 and 161 and the-lamp I52 to battery causes-the lamp I'62 to light. The replacement of the receiver 50 "at the substation AI allows the-relay I10 to're-' store -and,'fromground thru armatures I11 and 116 and the lamp I18 to battery,-cause the lamp [18 tolight. The two lighted lamps indicate to 'the operator that the call has beenended and 55 :tth-at the 'cord circuit A is to be disconnected "from thelines I232 and L34 Removal of the plug I53 from thejack I98 opens the circuit to the cut-off relay'IUil and the relay let. The cut-oil? relay I00 arestores and connects ground and the line relay I115 'to' the line L32 at armatures I02and Illl respectively. The relay I'Iiil restores and extinguishes the lamp I52 by opening its circuit :at rarmature I6I. Battery thru the winding of :the :relay I (it is disconnected from the contact r315and othersimilar contactsand from the lower conductor of "the jack I88 and multiples thereof and. the line L32 will now test not'busy to connectors such as connector D or to cord circuits such'as the cordcircuit A. Removal of the plug I19 from the jack I28 opens the circuit "to the :cut-o'fi relay I29 and the relay I15. The'cut-ofi relay I20 restores and connectsground and the 'line relay 125 to the line L34 at armatures I22 --and I2'I respectively. The relay I15 restores and Z5 extinguishes'the lamp {18 by opening its circuit 225 thru armature II.

at armature I16. Battery thru the winding of the relay I15 is disconnected from the contact 38I and other similar contacts and from the lower conductor of the jack I28 and multiples thereof and the line L34 will now test not busy to connectors such as connector D or to cord circuits such as the cord circuit A.

It may be noted that connections may be extended from the substantion MI to other substations such as the substations M2 or A2 in the same manner as described above for the connection from the substation MI to the substation AI and that connections may be extended in a like manner from the substation M2 to other substations.

Assume now that a call is to be made from the automatic substation A2. The receiver is removed at the substation A2 and battery thru the winding of the line relay I35, armature MI, thru the line L35, the substation A2 and armature I42 to ground operates the relay I45. The relay I45 energizes the relay I55 from ground thru armatures I46 and I52 and the winding of the relay I55 to battery. The relay I55 operates and at armature I58 disconnects the cut-off relay I40 from the lower conductor of the jack I48 and from the contact 318 and connects battery thru the resistor I59 to the lower conductor of the jack I48 and contact 318, and multiples thereof, to make the line L35 busy to connectors, such as the connector D, and to cord circuits such as the cord circuit A, at armature I56 ground is connected to contacts, such as the contact 230, in finders, such as the finder B, and thru resistor 232 to the distributor 235, and at armature I51 battery thru the winding of the cut-off relay I50 is connected to contacts, such as contact 226, in finders, such as the finder B.

The finder B is one of a group of similar finders having access to the substation A2. The distributor 235 selects an individual one of the finders and in response to ground thru a resistor, such as the resistor 232, causes the selected finder to hunt for a calling line. Assume now that the finder B has been selected for operation by the distributor 235.

Ground thru resistor 232, over a circuit previously traced, causes the distributor 235 to start the finder B and cause it to hunt for a called line.

The finder B first moves its wiper 234 over contacts such as contacts 23I and 230. In this case ground on the contact 233 causes the finder B to rotate its wipers 22I, 222 and 223 respectively, until in engagement with contacts such as contacts 224, 225 and 223 respectively, and at the same time disengage the wiper 234 from the contact 230. Assume now that the wiper 223 is engaged with the contact 226 to which battery is connected over a circuit previously traced. Battery extended thru the wiper 223 over the conductor 242 to the distributor causes the distributor to stop the hunting action of the finder B and operate the relay 280 to connect the line L35 thru to the selector C, thru wipers 22! and 222 and armatures 204 and 203. Ground thru armature 282, wiper 223, contact 225, armature I51 and the winding of the cut-ofi relay I to battery energizes the cut-off relay 550. The cut-off relay I50 operates closing a circuit from battery thru resistor I58 and armature I54 to the lower conductor of the jack I48 and contact 318, opening the circuit to the relay I55 at armature I52, and closing a holding circuit for itself from contact The relay I 55 restores disconnecting ground at armature I56 from the a 6 resistor 232 and the distributor 235, and closing a circuit to the cut-01f relay I40 from battery thru the resistor I59, armature I54, armature I58 and the winding of the cut-off relay I40 to ground. The cut-01f relay I40 operates disconnecting ground and the line relay I45 from the line L35 at armature I42 and I4I respectively.

The selector C is preferably of the well known Strowger type, responds to the first digit dialed at the substation A2, to position the wipers 236, 231 and 238 adjacent the level of contacts corresponding to the number dialed. During the interval between the first and second digits, the selector C operates automatically to select an idle line in the selected group of lines extending to the group of connectors in which the connector D is included. Assuming that the connector D is selected, the connection is extended thereto by way of the selector wipers 236, 231 and 238, contacts 239, 248 and 24E and the conductors 24, 25 and 23 and the connector D is prepared for the second and final digits. When the selector C is seized, the release relay 2H) is operated to complete, thru armatures 2I I and 20I, a holding circuit for the relay 200, and the relay 200 is extended thru contact 2| 2, wiper 238, contact 24! and conductor 23 to the connector D. A circuit may now be traced from battery thru the upper winding of the relay 355, contact 302, conductor 24, contact 239, wiper 235, armature 204, wiper 22I, contact 224, thru the line L35 and the substation A2, contact 225, wiper 222, armature 203, wiper 231, contact 243, conductor 25, contact 304, lower Winding of the relay 3IEI to ground. The relay 3I0 operates and at armature 3II closes a circuit to the relay 3I5, and thru ofi? normal springs 381 to the upper winding of the relay 320. The relay 3I5 operates and at armature 3I6 connects ground over conductor 23, contact 24!, wiper 238, contact 2 i 2., armatures 2H and 20I and the winding of the relay 280 to hold the same, at armature 3I1 closes part of the incomplete impulsing circuit, at armature 3I8 prepares a holding circuit for the relays 330 and 340, and connects battery thru resistor 353, armatures (H9 and 325, the lower winding of the relay 340 and armature 353 to the wiper 312. The relay 320 operates and at armature 32I prepares a circuit to its lower winding and the vertical magnet 368 in multiple. The relay 3I0 responds to the second digit and at armature 3II opens and closes a circuit to the lower winding of the relay 320 and the vertical magnet 383, which may be traced from ground thru armatures 3I I, 3H and 32I. At the first vertical step the oif normal springs 381 are opened thus opening the starting circuit to the upper winding of relay 328. The vertical magnet operates the wipers 310, 31! and 372 to the level corresponding to the dialed digit. The relays 3i 5 and 320 are slow to release and do not restore during impulsing.

After second digit has been received the relay 3I0 operates and at armature 3!! holds the relay 3I5. The relay 320, after a short interval, restores and at armature 32I prepares a circuit to the relay 350 and the rotary magnet 308 in multiple. The relay Sill responds to the final digit and at armature 3H opens and closes a circuit to the relay 3'50 and the rotary magnet 388 in multiple which may be traced from ground thru armatures 3I I, 3I1, 32!, 3'21, 353 to the winding of the relay 35B and thru armature 53! to the rotary magnet 368. The relay 350 operates, at armature 352 short circuits armature 321 to prevent interference with the rotary operationif V GEN. & BAT. to signal the substation M2.

the relay 325 operates during the same, and at armature 353 disconnects the lower winding :of

the relay 330 from the wiper 313 and connects the wiper 3l2 thru armature 343 and the winding of the relay 325 to ground. The relays 315 and 353 are slow to release and do not restore during impulsing. The rotary magnet steps the wipers to the contacts corresponding to "the dialed digit which in this case are assumed to be the contacts 382, 38 3 and 384 associated with the line L33. If the line L33 is busy, battery will be encountered 'on the lower conductor of the jack H3 and the contact 38 5. This battery may be supplied thru "the lower conductor of a plug, such as the plug 163, or by another connector, such as the connector D as will be subsequently described. Battery on the contact 334, thru wiper 312, armatures 353 and 3 53 and the winding of "the relay 325 to ground operates the relay 325. The relay 3'25 connects busy tone thru condenser 33'l, armature 328, contact 333 and condenser 335 to the calling line, opens the starting circuit to the relay 353 and the rotary magnet 358 at armature 327, and prepares its ownholding circuit at'armature 323. Shortly after the final digit has been received the relay 353 restores and at contact 354 closes a holding circuit for the relay 325 which may be traced from battery thru resistor 333, armatures 369, and 328, contact 333, armature 343 and the winding of the relay 325 to ground. The relay 325 remains operated and supplies busy tone "to the calling line until the calling line releases.

If battery is not connected to the contact 384, ground thru the winding of the relay H3, contact 333, wiper 3Y2, armatures 353 and 343 is connected thru the winding of the relay 325 to ground. Thus the relay 325 will not operate or, if it is operated, will release. When the relay 350) restores, after the final digit has been received, a circuit may be traced from battery thru resistor 363, armatures 353 and 323, the lower winding of the relay 333, armature 353, wiper 3T2, contact 383, and the winding of the cut-d relay Hi! to ground. The cut-01f relay l I 0 operates and disconnects ground and the line relay H from the line L33 at armatures [l2 and Hi respectively. The relay 343 operates its armature 333 first closing a circuit from battery thru the rotary magnet 338, upper winding of the relay 333, and armatures 333 and 3l3 to ground. The upper winding of the relay 343 operates the relay 3 53 in full, closing a multiple holding ground thru armatures 3M and to conductor 23, disabling the starting circuit to the relay 350 and the rotary magnet at armature 348, connecting battery thru resistor 363 thru armature 342 to the wiper 372 and the contact 334 to make the line L33 busy, opening the incomplete circuit to the relay 325 at armature 34-3, connecting ring back tone thru condenser .363, armature 341, contacts 333 and condenser 335 to the calling line, and connecting GEN. GRD; thru armatures 333 and 345, wiper 3'll, contact 383, thru the line L33 and the substation M2, contact 382, wiper 313, armatures 335 and 345 and the upper winding of the relay 333 to The relay 339 will not operate in series with the signalling device at the substation M2. When the receiver is removed at the substation M2 the upper winding of the relay 333 operates the armature 333. Battery thru the lower winding of the relay 330, thru armatures 333 and 3"? to ground operates the relay 333 in full, disconnecting the upper winding of the relay 330 from the wiper scribed in the foregoing for substation M2.

373 at armature 335 and connecting the wiper 31!] thru the upper winding of the relay 333 to battery, disconnecting ring back tone from the calling line at contact 333, disconnects the'wiper 3' from GEN. GRD. at armature 333 and extendingv the wiper 3?! thru the lower winding of the relay 333 to ground, preparing a multiple holding ground for its lower winding and the upper winding of the relay 343 at armature 332, and disabling the relay 353 and the rotary magnet 368 at armature 33!.

Battery thru the upper winding of the relay 333, armature 3 35 and 343, wiper 31G, contact 382, thru the line L33 and the substation M2, contact 333, wiper 31!, armatures 335and 334 and the lower winding of the relay 33-3 to ground operates the relay 333. The relay 333 reverses battery to the calling line at armatures 3i]! and 3133, closes a multipleholding ground to the lower winding of the relay 333 and the upper winding of the relay 330 at armature 335, and opens a part of the incomplete circuit to the release magnet 333 at armature 333. Transmission battery to the substation M2 is supplied thru the winding of the relay 333 and to the substation A2 thru the windings of the rotary 3E3. Voice currents between the two substations pass thru the condensers 385 and 336.

When the conversation is ended the receivers are replaced at the substations A2 and M2 thus allowing the relays 3H] and 333 to restore. Relay 3H3 opens relay 3S5 which shortly thereafter restores. The relay 333 restores, opening a multiple holding ground to the re1ays'330 and 340 at armature 335 and preparing a circuit to the release magnet 333 at armature 335. The relay 355, atv armature are opens the holding circuits to the relays 333 and 330, at armature 3E5 removes a multiple holding ground from the: conductor 23, and at armature 3!? completes the circuit to the release magnet which may be traced from battery over the'RLS. SIG. conductor, thru the winding of the release 353, off normal springs 35L armatures 333, 3!! and 3!! to ground. The relays 333 and 33!! restore, and the release magnet allows the switch Wipers to restore to normal position thus preparing the connector 1) for further operations. When the wipers reach their normal position, the ofi normal springs 38? are closed, preparing a starting circuit to the relay 323, and the off normal springs 35! are opened thus opening the circuit to the release magnet 333.

It may be noted that battery thru the resistor 363 is connected thru the lower winding of the relay 335 and wiper 372 to contacts, such as contact 384, at the time the relay 358 restores,

and that this battery is connected directly to such contacts subsequent to the operation of the relay 343. This battery serves as a busy indication to cord circuits, such as the cord circuit A, and to the connectors, such as the connecto D. The battery connected to the resistor 333 is of the same voltage used in the operation of the manual switching equipment, while the battery used for the other operations of the connector D is preferably of the same voltage customarily used for operating automatic switching equipment.

It may be noted that calls can be extended to other substations thru the connector D, such as substation Al, in the same manner as that de- If a call is extended from a connector, such as the connector D, to the substation Al battery over conductor 23 is extended to the lower conductor of the jack I28 and, thru armature I38 and the winding of the cut-off relay I20 to ground. The cut-off relay I20 operates, disconnecting ground and the relay I25 from the line L34 at armatures I22 and I2I respectively. No other equipment associated with the substation AI is operated at this time. Should the operator contact the upper conductor of the plug I19 to the lower conductor of the jack I28 at this time, current will flow from battery thru the lower conductor of jack I28, upper conductor of plug I79 and the upper winding of the relay III! to ground. This current flow thru the upper winding of the relay I10 is received in the operators telephone I72 thru the key IE9 as a busy indication.

In the line equipment used with automatic substations, such as the substation Al, the cutoff relay I20 and the line relay I25 are the same as the cut-off relay I and the line relay I respectively, while the relay I35 and the cutofi relay I36 are respectively the same as the line and cut-off relays customarily used in automatic systems employing finders, such as the finder B. If the relay I35 and the cut-off relay I30 are used in a full automatic system they are not associated with the relays I20 and I25. The relay I35 is connected thru armature I32 directly to one side of the line and ground thru armature I33 is connected directly to the other side of the line. The Winding of the cut-oil relay I39 is connected directly to the test conductor of the connector multiple, such as the conductor 20. The armature I53 is provided on the relay I50 for the same purpose. The battery connected to the line relay I25 and to the resistor I 39 is of the same voltage as the battery used for operatin the manual switching equipment while the battery connected to the cut-off relay I39 and the relay I35 is of the same voltage as the battery used for operating the automatic switching equipment.

The line equipment for a substation, such as the substation Mi may be easily modified for use with automatic switching equipment. Battery normally connected to the contact I09 is replaced by ground. The armature I06 is disconnected from the lamp I0! and is connected thru an armature, such as the armature I32, to a line relay, such as the line relay I35 and the cut-cit relay Int! is connected thru an armature such as the armature I33 to the lower conductor of the jack H38 and to the contact 375. A cutoff relay such as the relay I 30 is provided and connections made to the finders, such as the finder 13.

Having described my invention, what is considered to be new and is desired to be protected by Letters Patent will be set forth in the following claims.

What is claimed is:

1. In a telephone system, a line circuit, automatic switches having access to said line circuit, a first control conductor for said line circuit to which a potential of one character is connected to make said line circuit busy, a potential of one character, a potential of a difierent character, means for connecting said potential of one character to said first control conductor, a second control conductor extending from said line circuit to said automatic switches, means for connecting one of said switches to said line circuit,

means in a connected one of said switches for to said second control conductor for applying a potential of said one character to said first-control conductor to thereby make said line circuit busy. I

2. In a telephone system, a line circuit, two control conductors for said line circuit, two classes of automatic switches, means for connecting a switch of one class to said line circuit, means for connecting a switch of the other class to said line circuit, a relay in said line circuit, means for operating said relay over one of said control conductors responsive to the connection of a switch of said one class to said line circuit, means controlled by said relay for preventing the connection of a switch of said other class thereto,

and a second relay in said line circuit, means for operating said second relay over the other of said control conductors responsive to the connection of a switch of said other class to said line circuit, and means controlled by said second relay for preventing the connection of a switch of said one class to said line circuit.

3. In a telephone system, a subscriber line circuit, two classes of automatic switches and a manual switchboard having means for seizing said line circuit, a control conductor for said line circuit extending to switches of one of said classes and to said manual switchboard, a guarding potential and means for applying said guarding potential to said conductor from a switch of said one class in case said line circuit is seized thereby, means for applying said guarding poten-- tial to said conductor from said manual switchboard in case said line circuit is seized thereby, a source of guarding potential in said line circuit and means connecting said source to said conductor in case said line circuit is seized by a switch of said other class.

4. In a telephone system, line circuits individual to subscriber lines, two cut-off relays for each of said line circuits, automatic switches of two different classes, means for connecting a switch of either class to one of said line circuits, means responsive to the connection of a switch. of one class to one of said line circuits for operating one of the cut-off relays thereof to prevent the connection of another switch of either class to said one line circuit, and means responsive to the connection of a switch of the other class to one of said line circuits for operating both of the cutofi relays thereof to prevent the connection of another switch of either class to said one line circuit.

5. In a telephone system, a line circuit individual to a subscriber line, two cut-01f relays for said line circuit, automatic switches of two different classes, a manual switchboard, means for connecting a switch of either class to said line circuit, means for connecting said manual switchboard to said line circuit, means for operating one of the cut-off relays of said line circuit responsive to the connection of an automatic switch. of one of said classes thereto, means for operating said one cut-off relay responsive to the connection of said manual switchboard to said line circuit, and means for operating both of the cut-01f relays of said line circuit responsive to the connection of an automatic switch of said other class thereto, means including said one cut-off relay for making said line circuit busy to said automatic switches and said manual switchboard, and other means including both of said cut-off relays for making said line circuit busy to said automatic switches and said manual switchboard.

6. In a telephone system, subscriber line circuits terminating in bank contacts accessible tc autoa line circuit to thereby seize a line circuit and make the same busy, and means in one of said line circuits responsive to the connection of another of said automatic switches thereto for connecting a negative'p'otential to the bank contacts and the switching contacts terminating said one line circuit tomake said one line circuit busy.

7 7; In aswitching system, an automatic switch, a potential-- ofonepolarity, a potential or an opposite polarity, two control conductors, a first relay, a second relay having a winding", means for seizing said switch, means for operating said first relay responsive to the seizure of said switch, contacts on said first relay for connecting apotential of one polarity to one of said control conductors, means for connectinga potential of an opposite polarity thru the winding of said second relay to the other of said control conductors, means for operating said second relay, and a contact on-said' secondrelay for connecting said potential of opposite polarity directly to said other control conductor. 7

V 8. In aswitching system, an automatic switch, two control conductors, a first relay, a second relay having a winding, means for seizing said switch, means for operatingsaid first relay responsive to the seizure of said switch, a potential of one polarity, a potential of an opposite polarity, saidfirst relay bein'g'efiective in case it is operated to connect said potential of one polarity to one of said control conductors and to connect said potential of an opposite polarity thru the winding of said second relay to the other of said control conductors, means for operating said second relay, said last means including-said potential of opposite polarity and said other control conductor, said second relay effective upon operation for connecting said potential of opposite polarity directly' to said other control conductor and for connecting said potential of one polarity to said one control conductor. 9. In a telephone system, an automatic switch accessible to another automatic switch and havmg access to a plurality of outlet paths, a potential of one polarity, a potential of opposite polarity, means for connecting said other automatic switch to said one automatic switch, means in said one automatic switch responsive to the connection of said other automatic switch thereto for connecting a potential of one polarity to said other automatic switch to hold the same, and means in said one automatic switch for connecting a potentialof the opposite polarity to any one of said outlet paths, said last potential being effective for seizing and guarding said one outlet path.

10. Ina telephone system a connector switch accessible to automatic switches and having access to a plurality of line circuits, a potential of one polarity, a potential of an opposite polarity,

means for connecting one of said automatic switches to said connector switch, means for connecting said connector switch toany one of said line circuits, means in said connector switch-for 12" supplying a potential of one-polarity to a connected one of said automatic switches to" hold the san -and means in said connector switch for connecting a potential or an" opposite polarity to a connected one of s'a'id'line circuits to seize and guard said one line circuit.

11. In a telephone system, a plurality of line circuits, a plurality of automatic switches acces sible to calling ones of said line circuits and having access to called one of said line circuits, means for seizing one of said automatic switches from a calling one of said line circuits, a potential of one polarity, controlineans for connecting to said calling line circuit said potential of one polarity to hold said calling-line circuit, means in said seized switch for controlling said control means, means for connecting said seized one of said automatic switches to a" called one of said line circuits, a potential of opposite polarity, and means in said last mentioned automatic switch for connecting to said called line circuit, said potential of opposite polarity to seize and hold said called line circuit. 7 V

12. In a telephone system, a line circuit, an automatic switch, two different paths for establishing connections between said line circuit and said switch, two controlc'onductors in said switch, a potential of one polarity, means'eiiective'in case a connection is established betwen said line circuit and said switch over one of said paths for connecting said potential of one polarity to one of said control conductors to hold said line circuit, a potential of opposite polarity, and means in said switch effective in case a connection is established between said line circuit and said switch over the other of said pathsfor connecting said potential of opposite polarity. to the other of said control conductors to hold said line circuit.

13. In a telephone system, a line circuit, automatic switches and a manual switchboard having access to said line circuit, a first control conductor, a potential of one polarity, means for connecting said manual switchboard to said line circuit, means at said manual switchboard for connecting said potential of one polarity to said first control conductor to make'said line circuit busy in case said manual switchboard is connected thereto, a second control conductor, a potential of another polarity, means for connecting an automatic switch to said line circuit, means in an automatic switch connected to said line ciredit for connecting said potential of another pclarity to said second control conductor, and means in said line circuit responsive to' the potential connected to said second control conductor for connecting a potential of said one polarity to said first control conductor to thereby make said line circuit busy. :i V

SETH E PETERSON. MORRIS E. GRIFFINS.

7 REFERENCES than The following references are of record in the file of this patent: UNITED STATES PATENTS Number Name Date 1,393,429 Clausen Oct. l l, 1921 1,930,522 Keyser Oct. 17,1933 2,289,895 Abbott J ly 14, 1942 7 2,337,411 Peterson 1 13128.21, 1.943

V anone'y "Oct. 2194:; 

